1. Field of the Invention
This invention relates to a low-density polymeric composition and its uses, for example as low-voltage electrical insulation, cable jacket material, buoyancy-adjusting filling for a cable or harness, dielectric material between the inner and outer conductors of a coaxial electrical cable, or thermal insulation.
2. Introduction to the Invention
Buoyant cables described in U.S. Pat. No. 4,963,420 and U.S. Pat. No. 4,110,554 use hollow glass micro-spheres to achieve low density combined with crush resistance for use in deep underwater operations. The micro-spheres are either compounded in ethylene or propylene polymers of density between 0.90 and 0.94 g/cc and extrusion-filled into the cable structure, as in U.S. Pat. No. 4,963,420; or are used alone to fill the interstices of the cable structure, thus avoiding difficulties which may occur when compounding the mixture of polymers and micro-spheres, but introducing other problems associated with the loose packing of micro-spheres.